The invention relates generally to photonic crystals, and relates more particularly to electrical contacts for photonic crystal devices. Specifically, the present invention relates to a method and an apparatus for dynamic manipulation and dispersion in photonic crystal devices.
Photonic crystal-based structures possess a number of unique properties that may be useful as building blocks in photonic integrated circuits (PICS). The ability of photonic crystals to confine light down to scales on the order of a wavelength, as well as low-loss, sharp bends, suggests their suitability for waveguides that can be utilized for compact optical devices. Another notable attribute of photonic crystals is their unique tunable dispersion, which may be exploited to “slow” the velocity of light for interference-based devices, such as switches.
The material systems most suitable for photonic crystal devices are those that have a large refractive index contrast (e.g., silicon, gallium arsenide, germanium) and a low absorption coefficient, as these materials produce a large photonic band-gap. Conveniently, many suitable photonic crystal materials may also function as semiconductor materials, making opto-electronic integration a natural fit. There are many ways to achieve opto-electronic interactions; the most efficient method depends heavily on the properties of the material and the nature of the device. Mechanisms to induce an optical change from an electronic input include changing the refractive index by application of an electric field, injecting carriers, or thermo-optic effects. These interactions commonly require electrical contacts to be placed in the vicinity of the optical device. For example, contacts to apply a voltage to induce resistive heating in a waveguide, or contacts to allow current injection into a resonant cavity, must be placed near the optical device in order to function effectively.
To date, it has proven difficult to combine electronic control with high refractive index, high confinement systems without distorting the optical field and inducing unwanted absorption. Thus, efforts to integrate electronic control with photonic crystal devices are confronted with two competing concerns: (1) the need to place the electrical contacts as close to the optical mode as possible to achieve optimal control; and (2) the need to space the electrical contacts far enough away from the optical mode to minimize distortion and absorption.
Thus, there is a need for a method and an apparatus for dynamic manipulation and dispersion in photonic crystal devices.